I tried to upgrade Neuron from 7.4 to the newest version under Ubuntu (14.10 or 18.10). The program installs without problem bu not my old programs don't work anymore I got error mistake when launching them : 64-linux_gnu_ld :cannot find -lncurses and so the libnrnlech.la file failed
Did something change in the command ?

Which file did you use to install NEURON? nrn-7.6.1.x86_64-linux-py-36-35-27.deb, or nrn-7.6.1.tar.gz, both of which are locate in neuron.yale.edu/ftp/neuron/versions/alpha/ .
If you used the gzipped tar file, did an error message about ncurses appear during compilation?

Hello Ted,
Hope you're well.
I used the deb file: nrn-7.5x86_64.deb. I did not get an error at this stage.
It happens with any version (or flavour) of Ubuntu .
If I try to install an old version (7.4 or before) I got an error on Ubuntu 18 (missing dependencies) but it works on previous release of Ubuntu (14.10 and before)